The particle 了 (le) has a lot of uses. One of the most common is to express the completion of an action. This is called aspect, which is not the same as tense. Tense is about when an action happens: past, present or future. With regards to 了 (le), aspect is about whether the action is complete in a certain time frame.

Most Basic Pattern

The simplest way to use 了 (le) is to just put it after a verb. When there's nothing else after the verb, there are no complications!

Structure

Subj. + Verb + 了

Examples

他们 到 了 。Tāmen dào le.They have arrived.

我 买 了 。Wǒ mǎi le.I've bought it.

我们 都 去 了 。Wǒmen dōu qù le.We all went.

我 找到 了 ！Wǒ zhǎodào le!I found it!

Putting 了 After a Verb with an Object

Here is where things start to get slightly more complicated. If the verb has an object, 了 (le) can go directly after the verb to indicate completion, but there are a few other conditions that should be met.

When Time is Specified

It's a good idea to specify the time anyway, if you're still getting used to Chinese verbs not indicating tenses by themselves. When you do this, it's generally OK to put the 了 (le) right after the verb and before the object.

Examples

When 了 Comes After the Object

OK, so here's the tricky part. Even when indicating completion, the 了 (le) can sometimes go after the object. This is not a topic that can be covered in depth at the elementary level, but you should be aware that this does happen too.

Putting 了 After Consecutive Actions

So what happens if a whole string of things happened in the past? Do you have to put a 了 (le) after each one, just like we'd put each verb in the past tense in English? Good question! The short answer is that you only need one 了 (le).

To keep things simple, we'll make the first action "coming" or "going" somewhere, which will be followed by another action. So we'll be using 来 (lái) or 去 (qù) plus a place in each sentence, and then another action. For this type of "consecutive action," 了 (le) should be placed after the final verb (or verb phrase), which marks the completion of the entire sequence.

Completion in the Future

了 (le) can appear in sentences about the future as well as the past. What's important is whether or not the action has been completed, no matter what time frame we're talking about. This also means that this 了 (le) isn't used with habitual or continuous actions.